1. Field of the Invention
This invention relates to a torque sensor, and more particularly to a high accuracy torque sensor.
2. Description of the Related Art
U.S. Pat. No. 7,412,906 discloses a steering system torque sensor that includes an input shaft, an output shaft, and a collar member sleeved movably on the input shaft and formed with a pair of ramp portions defining camming surfaces. Upon application of a torque to the input shaft, the input shaft is rotated relative to the output shaft to result in rotation of the ramp portions relative to pin followers, thereby causing an axial movement of the collar member along the input shaft by a distance, which leads to a proportional change in a magnetic field and, thus, an voltage output corresponding to the torque.
However, a relatively high precision is required for forming the ramp portions, thereby increasing the manufacturing cost of the torque sensor. Furthermore, wear experienced between the ramp portions and the follower pins results in a decrease in the precision of the ramp portions after the torque sensor is used for a long time period. As such, the measurement accuracy of the steering system torque sensor is low.